The present invention relates to disk drives. In particular, it is directed to disk drives in which the head is located upstream of the actuator arm.
Disk drives are data storage devices that are commonly used in many applications. In a typical hard-disk drive, a disk enclosure houses a spindle that supports and spins a stack of disks and an actuator that positions a comb of head-carrying assemblies. At least one transducer element, (referred to here as a head) reads and/or writes data to and/or from each disk and is carried by each head-carrying assembly.
One of the challenges of disk-drive design is to maintain the head at a very precise location that is preferably a very small fixed distance above the disk. Variations in the height of the head from the disk, the radial location of the head over the disk, and the roll and pitch angles of the head increase the probability of read/write errors. An exceptional design would hold the head at a fixed height and orientation above the disk regardless of any conceivable disturbance.
Modern disk-drive design attempts to achieve these goals through the use of an air-bearing slider designed to fly over the spinning disk. The head is either formed as part of the slider, or is mounted to it. As the disk spins, the air adjacent to the disk is induced to rotate substantially with the disk. The slider flies in the induced flow. The aerodynamic forces generated on the slider are generally balanced by a suspension to which the slider is attached. A balance between the design aerodynamic forces on the slider and the restoring elastic forces imposed by the suspension helps to maintain the slider, and hence the head, at the desired fly height and angle.
Traditional disk drives are arranged as shown in FIG. 1. A shroud 105 partially encloses at least one disk 100 that is supported by a spindle 150 that rotates the disks. For convenience, FIG. 1 shows only a single disk although many more may be part of the disk stack. The disk 100 spins in a spinning direction 120. The air between adjacent disks (or if no adjacent disk exists, in the vicinity of the disk 100) is dragged with the disk 100, thereby inducing a flow 125 that rotates substantially with the disk 100. The head-carrying assembly 200 is comprised of an actuator arm 210, a suspension 230, and a slider, which is not shown in FIG. 1, but which would be attached to the suspension 230 in the vicinity of the distal end 204 of the head-carrying assembly 200. As mentioned earlier, a head would be mounted on, or be integral with, the slider. To position the head over the disk 100, the head-carrying assembly 200 is usually designed to rotate about a point in the vicinity of its proximal end 202. A rotary actuator rotates the head-carrying assembly 200 in response to signals received from an actuator electronics package, which determines exactly how much the head-carrying assembly 200 must rotate for the head to reach the desired position. Linear actuators, in which the head-carrying assembly is moved linearly to position the head over a desired radius of the disk, are currently less commonly used.
In the traditional configuration, the introduction of the head-carrying assembly 200 into the flow induced by the disk 100 distorts the substantially solid-body rotation of the flow. As seen in FIG. 1, the head-carrying assembly 200 blocks the smooth passage of the air. (As used herein, the word xe2x80x9cairxe2x80x9d denotes whatever fluid is between the disks.) The bulk of the air is channeled through the gap between the spindle 150 and the distal end 204 of the head-carrying assembly 200. Most of the remaining air is deflected outwardly. In practice, a small portion of the air will also squeeze between the head-carrying assembly 200 and the disk 100 or an adjacent disk (not shown) in the disk stack.
The traditional arrangement causes a number of problems. The flow that is channeled through the gap between the spindle 150 and the distal end of the head-carrying assembly 204 is traveling faster than the disk 100. Because turbulent fluctuations typically scale with flow speed, the increased speed likely implies increased turbulent fluctuation amplitude, and hence larger excitations of the head. In addition, some of the flow channeled through the gap has flowed alongside the edge of the head-carrying assembly 200 for an extended period of time. Turbulence created by the complicated interaction of the flow with the head-carrying assembly 200 will be swept along the suspension 230 and produce additional unsteadiness, which must be damped. The situation is dramatically worsened by the fact that the flow expands rapidly upon exiting the gap between the spindle 150 and the distal end 204 of the head-carrying assembly 200, thereby producing very high-intensity turbulent fluctuations in the vicinity of the head.
One way to circumvent this problem is to position the head upstream of the actuator arm. Positioning one head upstream of the actuator arm is disclosed as a side effect in various prior patents that employ multiple head-carrying assemblies between adjacent disks.
U.S. Pat. No. 5,218,496 to Kaczeus shows a pair of angularly offset head-carrying assemblies disposed between adjacent disks. The head on one head-carrying assembly magnetically cooperates with the lower surface of the upper disk and the head on the other head-carrying assembly magnetically cooperates with the upper surface of the lower disk. The patent mentions that the orientation of the sliders that support the heads on each head-carrying assembly is reversed in the design.
In U.S. Pat. No. 5,343,347 to Gilovich, a disk drive is disclosed in which the positioning relative to the flow between the disks of some heads and actuator arms are reversed from that of others. Gilovich does not address which of the heads are upstream of their actuator arms and which are downstream, nor does he address the fluid-mechanical implications of altering the upstream/downstream relationship between the heads and the actuator arms.
However, in U.S. Pat. No. 6,057,990, also to Gilovich, he indicates that a weakness in his earlier work was that in most cases at least two different and distinct heads would be required (column 1, lines 48-57). He states that he believes that no manufacturer in the industry constructs a transducer head that would accommodate a disk rotating clockwise with a head to the right of the spindle or a disk rotating counterclockwise with a head to the left of the spindle (column 1, lines 28-34). Analysis of these configurations reveals that such orientations correspond to situations in which the head is upstream of the actuator arm.
Considerable effort has been expended devising schemes to dampen the effects that the turbulent fluctuations have on vibrations of the head. In the current invention, exceptional reduction of head vibration is achieved by decreasing the turbulent fluctuations encountered by the head. Reorienting the head-carrying assembly relative to the flow induced by the spinning disks reduces the turbulent fluctuations.
The reoriented configuration is illustrated schematically in FIG. 2. In the novel configuration, the head-carrying assembly 200 is oriented such that, relative to the induced flow 125, each head (not explicitly shown, but ordinarily carried by the suspension 230) is disposed upstream of its actuator arm 210. The prior art discussed above shows some, but not all, of the heads oriented upstream of their respective actuator arms. The current invention is distinguished from the prior art by requiring that each head-carrying assembly 200 is oriented with its head upstream of its actuator arm 210.
Alternatively, the reoriented configuration can be described by considering the angle between two lines. A first line extends from the disk center 110 to the distal end 204 of the head-carrying assembly 200. A second line extends from the disk center 110 to the pivot 205 about which the head-carrying assembly 200 rotates. In the reoriented configuration, the angle 140 measured in the spinning direction 120 from the first line to the second line is less than 180 degrees for all head-carrying assemblies 200.
A similar geometric description of the reoriented configuration is applicable to both rotary actuators, as shown in FIG. 2, as well as linear actuators, as shown in FIG. 3. A first line is defined to extend from the disk center 110 to the head, a second line from the disk center 110 to the proximal end 202 of the head-carrying assembly 200. The angle 140 measured in the spinning direction 120 from the first line to the second line must be less than 180 degrees.
Compared with a traditionally configured disk drive, as shown in FIG. 1, preferred embodiments of the new configuration provide several beneficial effects. Because the head is upstream of the actuator arm 210, turbulence generated by the interaction of the flow with the actuator arm 210 is no longer convected directly towards the head. In addition, the channeling of the flow through the gap between the distal end 204 of the head-carrying assembly 200 and the spindle 150 is essentially eliminated. Therefore, the flow speed in the vicinity of the head is reduced. In addition, the high-intensity turbulence produced as flow expanded rapidly downstream of the gap in the traditional configuration is also greatly reduced.
The advantages of the preferred embodiments motivate another view of the invention as a method for reducing head vibrations in a disk drive. The reduction in head vibration is achieved by properly orienting each head-carrying assembly. The proper orientation requires the angle, measured in the spinning direction, between a first line that extends from the disk center to the distal end of the head-carrying assembly and a second line that extends from the disk center to the proximal end of the head-carrying assembly be less than 180 degrees.
Various embodiments of the invention also include a specially designed disk drive suspension that is well suited for orientations in which the head is upstream of the actuator arm. The new suspension includes a load beam, a flexure, and a motion limiter. The load beam is typically attached to the actuator arm. The flexure has a proximal end that is mounted to the load beam and an opposing distal end. Flexure legs near the flexure distal end support a gimbaled region, which has its distal end coupled to the flexure legs. A slider is typically fastened to the gimbaled region. The suspension also includes a motion limiter that is fixed to the gimbaled region and interacts with the load beam. Unlike traditional suspensions in which the flexure legs are in tension, upstream orientation of the head typically places the flexure legs in compression. To help avoid buckling of the flexure legs, the motion limiter of the new suspension limits not only the displacement of the gimbaled region away from the load beam (as is done with conventional motion limiters), but also the displacement of the gimbaled region towards to the flexure proximal end. In this way, the motion limiter relieves the flexure legs of excessive compressive loading.
Additional features and advantages of the invention will be set forth in part in the description that follows, and in part will be obvious from the description, or may be learned by practice of the invention. Various embodiments of the invention do not necessarily include all of the stated features or achieve all of the stated advantages.